Machine for grinding taps



0. S. BICKFORD.

MACHINE FOR GRINDING TAPS.

APPLICATION FILED MAY 10, 1920.

o r 2 7 0 f my 9 T. @E An Nw M m Wm mm dw w e m m m h a O. S. BICKFORD.

MACHINE FOR GRINDING TAPS.

APPLICATION FILED MAY 10, 1920.

L DQZ SD Patented Jan. 3 1922 W 0 fl 2 SHEETS-SHEET 2.

IN VENTOR, wmm 61 522mm;

A TTORNEY.

ORAMEL S. BICKFORD, OF GREENFIELD, MASSACHUSETTS.-

MACHINE FOR GRINDING TAPS.

Application filed May 10,

T 0 all whom it may concern:

Be it known that I, ORAMEL S. BICKFORD, a citizen of the United States of America, residing at Greenfield, in the county of Franklin and Commonwealth of Massachusetts, have'invented certain new and useful Improvements in a Machine for Grinding Taps, of which the following is a specificationf This invention relates to improvements in machines for grinding or sharpening taps. Heretofore it has been the common practice to grind the cutting lands or flutes of a tap by holding the teeth against a revolving stone, as an emery wheel or grind stone. This operation is not only slow, but very inaccurate, as some of the teeth are liable to be of different radial lengths and also of different degrees of backing off or tooth clearance.

My improvement is designed to overcome these objections and to provide means for automatically and successively grinding all of the teeth or flutes, and at the same time to automatically produce the necessary tooth clearance or backing off space for each tooth.

Broadly considered, the invention comprises a horizontally slidable or movable carriage for receiving the tap to be ground, with devices for simultaneously rotating the tap and for oscillating the tap towards and away from a suitable grinding wheel to provide the necessary clearance, also means for reversing the direction of movement of the carriage, and devices for placing the axis of the tap, being ground, at an angle to the line of travel of the carriage, whereby the tap ma be ground on any desired taper or angle.

eferring to the drawings: Fig. 1 is a plan view showing the parts arranged in parallel relation to each other.

Fig. 2 is a side elevational view of Fig. 1

showing the fixed and movable frame members, the gears for operating the lead screw,

the spring for holding the rockable frame against the stop, and the hand screws for holding the adjustable head in place and for locking it after it is turned at an angle.

Fig. 3 is a detail view on the line 3-3 of Fig. 1, showing the manner of mounting the slidable tap-carrying frame on the fixed or lower frame; the guide rods and the lead screw being shown in section.

Fig. 4 is a sectional plan view on the line 44 of Fig. 2 showing the pivotal connection between the frame or part that supports Specification of Letters Patent.

Patented J an. 3, 1922.

1920. Serial No. 380,186.

the tap and the under frame which moves wlth the tap carrying frame, also the arcsh'aped slot construction which permits the ad uStment of one frame relative to the other.

Fig. 5 is a transverse sectional view on the line 55 of Fig. 2 showing the gear shlft connection between the shaft which rotates the tap and the lead screw for reversing the same.

Fig. 6 is a transverse sectional view on the line 6-6 of Fig. 2, showing the eccentric devices for imparting a rocking movement of the tap towards and away from the grinding wheel.

Fig. 7 is a view similar to Fig. 6 but showing the parts in their rocked or tipped position towards the wheel.

Fig. 8 is a view illustrating the position of the lands or flutes of the tap with relation to the grinding wheel, and before the tap is rocked or moved by the eccentric cam.

Fig. 9 is a view showing the position of the tap after being tipped towards the wheel, and illustrating the wheel in the act of grinding the heel part of the lands or flutes for the clearance.

Referring to the drawings in detail: 1 designates the fixed part of the machine having the upwardly extending part 2 which is formed with the integral and inwardly extending portions 3 and 4. These portions are formed with openings in which is slidably mounted the rod 5, which rod is secured at its ends in the ears 6 and 7 that form part of the slidable plate 8. This plate, as shown in Figs. 2 and 3, is formed with the depending ears 9 and 10 on the rear lower side. In these ears is secured the rod 11 which slides in openings in the upwardly extending ears 12 and 13 of the base piece 1 (see Fig. 2). Mounted in the forward end of the arm 3 is" an internally threaded block 14: which receives the lead screw 15. 16 is a pin for securing the block 14 in place. The lead screw 15 is rotatably supported in the arms 7 and 17; these arms being integral with the plate 8. lVhen the lead screw 15 is rotated it will be seen that the plate 8 will move relative to the base-piece 1 since this plate is supported in the base piece by means of the rods 5 and 11, as already described. The means for rotating the lead screw will be described later. 18 designates a swinging table or plate that is pivotally connected to the slidable plate 8 by means of the pin 19.

The shape of the table 18 is shown in plan view in Fig. 4. For retaining the table 1 8 in different positions of adjustment relative to the plate 8, an arc-shaped slot 20 is formed in the plate 8 (see Fig. 4). In thls slot is located a pin 21 having a thread at its lower end to receive a clamping knob or nut 22. The right hand end of the table 18 is formed with a longitudinal slot 23 for the purpose of adjustably securing the head 24 on the table by means of the knob 25 which engages the threaded pin 26 that is located in the slot 23. The rear end of the head 24 is formed with upwardly extending bosses 25 in which is located one end of the rotatable rod 26. The other end of the rod 26 is located in the boss 27 which is an integral part of the right hand end of the plate 18. This rod is provided with a collar 28 which is pinned thereto for retaining it in place. Secured to the outer end of the rod is an arm 29 in the upper end of which is located the center pin 30 for receiving the cone shaped recess in the end of the tap to be sharpened, which is indicated at 31. 32 designates .a screw for securing the arm 29 to the rod 26.

Referring now to the structures for rotating and holding the tap in place, the devices for rocking the same to give or provide an eccentric relief or clearance to the lands or flutes, and for operating the lead screw 15 for moving the tap along across the face of the grinding wheel 33. 34 designates a rockable member which is formed with an upwardly extending bearing part 35 in which is located the operating or driving shaft 36 to which the handle 37 is attached. The lower and rear portion of the member 34 is formed with a boss part that is located between the upwardly extending bosses 25 of the head 24 (see Fig. 4). As this part of the member 34 is below the bearing 35 and behind the part 25 (see Fig. 6) it does not appear on the drawings. The forward end of the rockable member 34 is formed with the two spaced bearings 39 and 40 for the shaft 41, which is connected to the lead screw 15 by means of the universal joint 42. The shaft 41 is rotated by means of the gear 43 which, has a splined connection therewith. This gear is driven from the gear 44 on the driving shaft 36 through either one of the gears 45 or 46, which are mounted on'the plate 47 (see Fig. 5) by means of the studs 48 and 49. A pin 50 is attached to the upper end of the plate 47 for moving it towards the gear 44 as shown by the arrow 51. The gear 45 is always in mesh with the gear 43. -When the gear 46 is thrown into mesh with the gear 44 the gear 45 is moved out of mesh with the gear 44 and the direction of rotation of the shaft 41 will be reversed. For holdin either one of the gears 45 or 46 in mesh with the gear 44 the plate 47 is formed with two notches 52 and 53 to receive the upper end of the holding latch 54, which is pivotally attached to the member 34 by means of the pin 55. In the position of the gears shown in Fig. 5, the shaft 41 and lead screw will be driven in the same direction as the shaft 36, and the carriage carrying the tap will be fed forward, that is to say towards the left hand end of the machine, when the gear 46 is in mesh with the gear 44 the tap will be returned when the shaft is rotated in the same or original direction.

Secured to the shaft 36 is a cupor bellshaped center piece 56 for receiving the squared end of the tap.

For imparting a rocking or eccentric movement to the tap while the lands or teeth are being ground during its rotary and advancing movement across the face of the wheel, a cam plate 57 having four lobes or elevations is secured to the shaft 36. 'This plate is secured in place by means of the set screw 58. 59 is a pin which is threaded through the arm 24 of the head 24, its inner end 59 bears against the face of" the cam 57, as shown. It is locked by means of the nut 60. It will therefore be seen that when the shaft 36 is rotated by the. crank 37, the fixed pin 59 will rock the member 34 from the.

position shown in Fig. 6 to that shown in Fig. 7 the angle of movement being indicated by the lines at 61. This rocking or eccentric movement of the member 34 causes the tap not only to be moved towards the grinding wheel but at the same time causes" the wheel to produce the necessary clearance of the teeth of the lands or flutes, as shown in the position of the tap at the beginning and ending of the rocking movement in Figs. 8 and 9. The clearance is indicated by the curved line 62. A coiled spring 63 is attached to the head 24 and to the rocking frame 34, respectively, as shown. It is for holding or drawing the frame 34 constantly against the screw 59.

- The complete operation maybe described as follows: T

The entrance or point end of the tap 31 is placed on the center pin 30; the head 24 is then moved towards the left until the squared end of the tap enters the bell or cone-shaped centering socket 56, the slots 56 causing the tap to seat in the socket. The head 24 is now clamped to the plate 18 by means of the knob 25. If a guide point is to be ground, that is to say a cylindrical surface that is parallel to the axis, the other knob 22 is loosened and the table 18 swung about the pin 19 bringing it into parallel relation or alignment with the main base 8. Both tumbler gears 45 and 46 are thrown out of mesh by disengaging the latch 54 from the notches 52 and 53 in the plate 47, a spring not shown serving to draw the gears away from the gear 44. The cam plate 57 is loosened from the shaft 36 and will remain in the position as shown in Fig. 6 and will be inoperative. The shaft 36 is now rotated with the end of the tap against the grinding wheel. This operation will. of course, grind withoutany relief. If relief or clearance is desired the cam 57 is tightened by turning screw 58 when it will operate against set screw 59. The plate 3-1 is moved forward to bring the gear 45 into mesh with the gear 44. This causes the lead screw 15 to be operated, moving the tables 8 and 18 together with the tap 31 across the grinding face of the wheel, meanwhile as the handle is rotated the cam 57 imparts a rocking movement to the tap. The universal joint permits the frame 34 to rock. The rocking movement caused by the cam 57 is imparted to the shaft 26 by means of a stud engaging the spline 26 in the shaft 26, which in turn, through the arm 29, carries the tap for ward against the wheel. The rocking members, therefore, include the frame 34, shaft 41. shaft- 26. arm 29, and tap 31. This rocking and eccentric movement therefore causes the proper clearance to be produced at the rear ends of the teeth of the tap as shown in Figs. 8 and 9. After the tap has been moved its length across the wheel, the tumbler gear 45 is disengaged and gear 46 is thrown into mesh with the gear 44 and the handle rotated in the same direction. The direction of rotation of the lead screw 15 is now reversed, and the tap carried towards the right hand.

If a taper is to be ground the knob 22 is loosened and the table 18 swung about the pin 19 until the proper angle is reached (see Fig. 4), when the knob is tightened to clamp the tables 8 and 18 together. The rotation of the shaft 36 causes the same operations as already described.

From this description it will be seen that I have produced a machine for grinding or sharpening the lands of a. tap by simultaneously imparting a rotary and eccentric movement thereto and about its own axis to give proper clearance to the teeth, and one whereby each and all of the cutting lands when ground will be the same radial distance from the axis of the tap, and the tap 31 is always rotated in the same direction.

\Vhat I claim is:

1. A machine for sharpening taps and like tools by grinding, the combination, of means for rotatably supporting the tap and simultaneously imparting a motion thereto corresponding to the number of flutes and which is eccentric to its axis and towards and away from a grinding wheel and means for continuously rotating the tap during the grindmg process.

2. In a tap grinding machine, the combination, a fixed and movable member, means for rotatably supporting the tap on the movable member, means for continuously rotating the tap, means for automatically imparting a motion to the tap that is eccentric to the axis of the tap and simultaneously with the continuous rotation of the tap, means for feeding the tap in a longitudinal direction and means for placing the tap at an angle to its line of motion While being ground including a lead screw, a universal joint between the lead screw and the tap operating means.

3. In a tap grinding machine, the combination, of means for continuously and rotatably supporting the tap, means for imparting an eccentric motion to the tap relative to its axis during the rotation of the same and including a cam located on the supporting means and rotated with the tap, a stop, means for holding the cam and tap supporting means against the stop to impart the eccentric motion to the tap, and means for continuously rotating the ta during the grinding process, a carriage or supporting the tap and means for reversing the carriage comprising a plate, gears thereon, connecting means between the gears and the tap rotating means, and means for engaging either one of the gears with the tap rotating means.

4. In a machine for grinding the lands of a tap, the combination, of means for rotatably supporting the tap while being ground and for simultaneously imparting a motion thereto which is eccentric to its axis for the purpose of grinding all of the lands equi-di'stant from the axis of the tap and for producing a clearance at the back of the cutting teeth, said means including a cam having a plurality of radially arranged letoif shoulders and a stop engaging the shoulders.

5. In a machine for grinding the lands of a tap, the combination, of means for rotatably supporting the tap while being ground and for simultaneously imparting a motion thereto which is eccentric to its axis for the purpose of grinding all of the lands equi-distant from the axis of the tap and for producing a clearance at the back of the cutting teeth, said eccentric motion being produced by means of an eccentric having as many lobes as the tap has flutes, as described.

6. In a tap grinding machine, the combination with a movable carriage for supporting the tap, of means for rotating the same, means for moving the carriage in a direction parallel to the axis of the tap or at an angle thereto, means for reversing the direction of travel of the carriage including a gear on the member that rotates the tap, a gear on the carriage operating means, a pair of idler gears between said gears and means for moving either one or the other of the idler gears into operative relation with the gear on the tap operating means.

7. In a tap grinding machine, the combination with a movable carriage for supporting the tap, of means for rotating the same, means for moving the carriage in direction parallel to the axis of the tap or at an angle thereto, means for reversing the direction of travel of the carriage including a gear on the member that rotates the tap, a gear on the carriage operating means, a pair of idler gears between said gears and means for movlng either one or the other of the idler gears into operative relation with the gear on the tap operating means, and means for simultaneously imparting an eccentric motion to the tap towards and from the grinding element.

8. In a tap grinding machine, the combination, with a base member having a curved slot therein, a carriage for rotatably supporting the tap to be ground, a lead screw for moving the carriage, means for operating the screw including a universal joint therein, means for reversing the direction of the rotation of the screw including a trainof gears, means for retaining the gears in operative relation, said slot permitting the tap to be ground on a taper, as described.

9. A machine for grinding taps, the combination with a rockable supporting member for a tap while being ground, of means for continuously rotating the tap while being ground, a grinding wheel, a cam having as many eccentrically arranged lobes as there are rows of flutes on the tap and rotatable therewith, said cam having let-ofi' shoulders, a stop engaging the eccentrically arranged lobes of the cam for causing the supporting member to move the tap toward the grind ing wheel and a spring for returning the tap and cam, whereby a clearance is produced back of the cutting edges of the teeth of. the tap which is similar to the eccentric shape of the cam and for adjusting the. tap sugporting members. for forming a tapered en O-RAMEL S. BICKFORD. 

